In recent years, the speed of networking hardware has increased by two or three orders of magnitude, enabling packet networks such as Gigabit Ethernet and InfiniBand™ to operate at speeds in excess of 1 Gb/s. Network interface adapters for these high-speed networks typically provide dedicated hardware for physical layer and data link layer processing (Layers 1 and 2 in the Open Systems Framework model). This hardware is capable of operating at wire speed, i.e., transmitting and receiving packets at the full, specified speed at which the network itself is capable of carrying data.
Higher-level protocols, however, are still processed for the most part by software running on host CPUs (central processing units) connected to the network. Common protocols of this sort include network layer (Layer 3) protocols, such as the Internet Protocol (IP), and transport layer (Layer 4) protocols, such as the Transport Control Protocol (TCP) and User Datagram Protocol (UDP), as well as protocols in layers 5 and above. Efforts to reduce the stack overheads of standard protocols used in packet networks, such as TCP/IP, have yielded only moderate improvements. Increases in the speed of host processors and memory access have not kept pace with the increases in network speed. As a result, software processing of protocol stacks has become the key bottleneck in packet network communications.